Identification
The corn earworm is a moth caterpillar that varies in color from green and brown to pink and yellow, with light and dark stripes along its body. Fully grown larvae reach 1.5-2 inches in length. The adult moth has a wingspan of about 1.5 inches and is light tan with dark markings. This pest is found throughout North America, particularly in regions with corn, tomato, and cotton crops.
Lifecycle & Reproduction
Corn earworms undergo complete metamorphosis. Females lay up to 1,000 eggs singly on host plants. Eggs hatch in 2-5 days, and larvae go through five to six instars over 2-4 weeks before pupating in the soil. The pupal stage lasts 10-14 days in summer but can overwinter in colder regions. Multiple generations occur per year in warm climates.
Habits, Diet & Behavior
Corn earworms are highly destructive feeders, consuming the reproductive structures of plants such as corn ears, tomato fruit, and cotton bolls. They are nocturnal, feeding primarily at night. The larvae burrow into plant structures, making them difficult to detect until significant damage occurs. Adult moths feed on flower nectar.
Where You’ll Find Them / Typical Locations
These pests are commonly found in cornfields, vegetable gardens, and cotton farms. They infest corn ears, tomato fruit, soybean pods, and other soft plant structures. Eggs are laid on leaves and silk threads of corn plants, and larvae burrow into fruiting structures.
Threats & Danger
Corn earworms cause severe economic damage to crops by feeding on kernels, fruit, and cotton bolls. Infestations reduce crop yields and quality, leading to financial losses for farmers. Larvae can also introduce fungal infections into damaged crops, exacerbating the damage.
Prevention
- Rotate crops annually to disrupt the pest’s lifecycle.
- Use resistant crop varieties when available.
- Encourage natural predators such as parasitic wasps and lacewings.
- Apply row covers to protect young plants.
- Time plantings to avoid peak moth activity.
Signs of Infestation
- Holes and frass (excrement) inside corn ears and tomato fruit.
- Silk damage and incomplete kernel development in corn.
- Damaged cotton bolls with feeding tunnels.
- Increased sightings of adult moths near crops.
- Stunted or deformed fruit due to larval feeding.
How to Get Rid of It
- Handpick and destroy larvae when found.
- Apply Bacillus thuringiensis (Bt) to target larvae.
- Introduce biological controls such as Trichogramma wasps.
- Use pheromone traps to monitor and reduce moth populations.
- Apply insecticides labeled for corn earworm control when necessary.